The Elements and Uses

Both of these elements are silver-white lustrous metals with high melting (ruthenium 2310°C, osmium 3900°C) and boiling (3900 and 5510°C, respectively) points. As usual, the 5d metal is much more dense (ruthenium 12.45, osmium 22.59gem-3) both adopt hep structures osmium is the densest metal known. The metals are unreactive, insoluble in all acids, even aqua regia. Ruthenium tends to form a protective coating of the dioxide and is not attacked by oxygen below 600°C nor by chlorine or fluorine below 

Powdered osmium is slowly attacked by oxygen at room temperature, yielding 0s04 (though not below 400°C if in bulk). Osmium reacts with fluorine and chlorine at about 100°C. Both metals are attacked by molten alkalis and oxidizing fluxes. 

Ruthenium nowadays finds many uses in the electronics industry, particularly for making resistor tracks. It is used as an ingredient in various catalysts and, importantly, in electrode materials, e.g. Ru02-coated titanium elements in the chloralkali industry. Osmium tetroxide is a very useful organic oxidant and, classically, is used as a tissue stain. Both elements are employed in making certain platinum alloys. 

Both palladium and platimun are shiny, silvery metals (with ccp structures), easily drawn and worked when pure. Palladium has the lower melting and boiling points (1552 and 3141°C, respectively) the corresponding figures 

The main uses of palladium [13] are in the electronics and electrical industries, in circuitry and in dental alloys. It finds many catalytic applications in industry, as well as in diffusion cells for the synthesis of hydrogen, and in automobile catalysts. Jewellery and three way auto-catalysts are the principal uses of platinum, which fulfils a wide range of roles in the chemical industry. 

Fuel cells essentially reverse the electrolytic process. Two separated platinum electrodes immersed in an electrolyte generate a voltage when hydrogen is passed over one and oxygen over the other (forming H30 and OH , respectively). Ruthenium complexes are used as catalysts for the electrolytic breakdown of water using solar energy (section 1.8.1). 

Both rhodium (m.p. 1976°C, b.p. 3730°C) and iridium (m.p. 2410°C, b.p. 4130°C) are unreactive silvery metals, iridium being considerably more dense (22.65gcm ) than rhodium (12.41 gcm ), the densest element known apart from osmium. Both form fee (cep) lattices and, like the other platinum metals, are ductile and malleable. Neither is affected by aqua regia and they only react with oxygen and the halogens at red heat. 

The main use of rhodium is with platinum in catalysts for oxidation of automobile exhaust emissions. In the chemical industry, it is used in catalysts for the manufacture of ethanoic acid, in hydroformylation of alkenes and the synthesis of nitric acid from ammonia. Many applications of iridium rely on 

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The creep curve for polypropylene at 4.2 MN/m (Fig. 2.5) is to be represented for times up to 2 X 10 s by a 4-element model consisting of a Maxwell unit and a Kelvin-Voigt unit in series. Determine the constants for each of the elements and use the model to predict the strain in this material after a stress of 5.6 MN/m has been applied for 3 x 10 seconds. 

The formula of a chemical compound gives the symbols of the elements and uses subscripts to show the relative numbers of atoms of each element in the compound. 

The best overall results are obtained by calibrating with single-bond energies for the elements, and using the arithmetic mean ... 

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